Definitely grab the 'most' storage you can if he's into shooting the video. It takes up a good chunk of space, and if he's editing and saving those edits along with the original it'll add up quick! I bought my son (8) an iPod Touch--the latest version for Christmas last year. He's taken extremely good care of it, and prefers it out of the case. We take it out of the house in a neoprene sleeve, but he uses the wristband....and it's remarkably scratch free and blemish resistant (it's black!). I'm actually extremely surprised. Other than the occasional 'booger wipe' from the screen (we carry a microfiber cloth)...it's been his favorite 'thing' since. We use iMessage with him and F/T as you're considering (entire extended family including a couple of his cousins)---grandparents and of course, mom and dad

. It's worked very well. The new iTouch is extremely nice---and very quick with an excellent display (in comparison to the generation previous). He's a bit young to be 'in to' video editing but he take plenty of pics and vids---and many turn out pretty damn good! We've been impressed. We also allow him to play games, etc....and some of these new games are pretty big, 1-2GB in some of the RPG/Racing/EA games. (He and I love playing 'Madden' and 'Tiger Woods' as well as several other mulitplayer games together). When necessary, if he needs, he can lock in to my wife or I's LTE signal if he needs connectivity away from home or 'hot spots'.
Interesting---I'm pretty liberal when it comes to electronics for my 8 year old son...but I've yet to see any of the third graders with a 'phone' yet. I go to the classroom twice a month to 'help' out for a couple of hours...and possibly, if they do have them they're safely stashed and turned off during school hours, as I can see it being a good tool if the parents are working odd hours or picking up/dropping off in different areas, etc....but was she in 'company' @ 8 years old with a phone? Or was she in a unique situation?
I seriously considered this past upgrade (I went 5--->5s, gave the 5 to my wife and sold her 4s) giving him the 4s but after much debate with my wife and considering the situation (I'm home when he gets out of school and my wife is home in the mornings with him to get him to the bus/school), we decided to wait another year or two.
I'm genuinely curious and honestly HOPE you don't think I'm judging you or your parenting in the least!!! LoL---quite the opposite, I'm actually kind of excited to 'win' the debate with my bride
(**We've been married 15 years and it took a while, but hit the jackpot with our son...he's well behaved, participates if five sports that I get to coach two of them in....and excels in the classroom as well as socially. We've only got one and it's always scary----everything you do in life; drive, fish, hunt or open a business...you need a license and can usually find a 'manual'! With one (child), it's a shot it the dark and a bit scary raising them....I don't want to be conservative, I want him to grow up with technology and hence he 'owns' the original iPad, the Touch...and is allowed to play certain Wii, XBox and PS3 games in his spare time or when it's just miserable in Alaska

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Genuinely curious though about the 'phone'....possibly a thread in the iPhone section would be the way to go though....to the OP, IMHO, you're on the right track!
J